1. Field of the Invention
The present invention relates to a dust seal device of a linear guide apparatus used in a machine tool, an industrial machine, and the like, and, in particular, to an improvement in the attaching structure of side seals and under seals which are components of the dust seal device.
2. Description of the Prior Art
With reference to FIG. 18, generally, a linear guide apparatus includes a long, axially extending guide rail 1 and a slider 2 having a substantially inverted U-shaped cross section and movably straddling the guide rail 1. The guide rail 1 has ball rolling grooves 3 formed in both side surfaces. A main body 2A of the slider 2 has ball rolling grooves 5 formed in inner surfaces of both side walls 4 so that the ball rolling grooves 5 respectively oppose the ball rolling grooves 3 of the guide rail 1 as shown in FIG. 19. A plurality of balls 6 are loaded in the opposed ball rolling grooves 3 and 5 such that the slider 2 is movable in an axial direction through the rolling of the balls 6. With the movement of the slider 2, the balls 6 interposed between the guide rail 1 and the slider 2 are moved while rolling to an end of the slider main body 2A. In order to continuously move the slider 2 in the axial direction, it is necessary to circulate the balls 6. Accordingly, a through bore 7 is formed in each of the side walls 4 of the main body 2A as a ball return passage. At the same time, end caps 2B having a substantially inverted U-shaped cross section are attached to opposite ends of the main body 2A. A pair of U-shaped curved paths 8 are formed in each of the end caps 2B to respectively bring the ball rolling grooves 3 and 5 into communication with the ball return passage 7. As a result, an endless ball circulating path is formed by the ball rolling grooves 3 and 5, the curved path 8, and the ball return passage 7. Furthermore, as shown in FIG. 18, the letter g denotes a grease nipple and, in FIG. 19, the letter H denotes a retainer for preventing the balls 6 from falling off when the slider 2 is removed from the guide rail 1.
When foreign matter, such as dust, chips, cuttings, and the like, intrudes into a gap between the guide rail 1 and the slider 2 straddling the guide rail 1 and is deposited on the ball rolling grooves and the like, the smooth movement of the balls 6 is disturbed. Accordingly, a side seal 10 is usually attached by small screws n to an outer end surface 2c of each end cap 8 to prevent the foreign matter from intruding from opposite end portions of the slider 2. At the same time, under seals 11 are attached to lower surfaces of the slider 2 to seal gaps between the side surfaces 1b of the guide rail 1 and the lower surfaces of the slider 2 and to thereby prevent foreign matter from entering from the lower gaps.
FIG. 20 shows an example of a prior art structure for attaching the side seal 10 and the under seal 11.
The side seal 10 has an inverted U-shaped front shape similar to that of the end cap 2B and is formed by molding a nitrile rubber on a steel plate. As a result, a rubber seal portion 12 is formed on an inner edge of an opening 21. Furthermore, inserting bores 14 are formed in an outer periphery of the rubber seal 12 in registration with screw inserting bores 13 formed in the end cap 2B. Reference number 16 denotes a nipple fixing bore which is formed in registration with a grease nipple fixing screw bore 15 formed in the end cap 2B. Small screws n are inserted through the inserting bores 14 and are tightened into engagement with the screw inserting bores 13. In this manner, the side seal 10 is fixed in place and seal lips L are slidably in contact with an upper surface la and side surfaces 1b of the guide rail 1 to seal opposite end sides of the slider 2.
Each under seal 11 is formed of an elastic sheet of a rectangular strip shape and has a length substantially equal to the length of the slider main body 2A, and a width slightly larger than the width of the lower end surface 17 of the slider main body 2A. Three fixing bores 18 are formed in the under seal 11 at spaced intervals in an axial direction. On the other hand, rivet bores 19 corresponding to the fixing bores 18 are formed in each lower end surface 17 of the slider main body 2A. The under seal 11 is applied to the end surface 17 of the slider main body 2A and fixed in place by inserting rivets 20 into the rivet bores 1 after passing through the fixing bores 18. A seal lip L of the fixed under seal 11 is slidably in contact with the side surface 1b of the guide rail 1 to provide sealing of the lower side of the slider 2.
However, in such a prior art dust seal device, or a dust seal structure of the side seals and the under seals of a linear guide apparatus, the following problems are encountered.
Each of the side seal 10 and the under seal 11 achieves the sealing effect only by an elastic deformation of the rubber material. As a result, due to non-uniform properties resulting from manufacturing and assembling processes, a seal clamping margin is excessively large and the operability is deteriorated by an increased frictional resistance. Furthermore, the rubber wears and the amount of elastic deformation is decreased. Thus, the sealing effect is lost at an early stage of use.
The side seal 10 is unitary molded by wrapping a mandrel of a steel plate with a rubber. As a result, a dimensional error often occurs and the contact with a surface to be sealed becomes non-uniform and partial wear is apt to result.
The under seal 11 is fixed by rivetting. Thus, the number of operations and the number of assembling processes are increased. In addition, when the pitch between the fixing bores 18 of the under seal 11 and the rivet bores 19 deviates, the under seal 11 becomes wavy. Further, when the intensity of caulking of the rivets 20 is too large, an edge of the under seal 11 will be turned. Thus, the assembling is unstable and the sealing properties become non-uniform.